..Our work paves the way for the realization of a MDI-QKD network, in which the users only need compact and low-cost state-preparation devices and can share complicated and expensive detectors provided by an untrusted network server. ..

..By scanning the driving frequency of a LiNbO3 phase modulator in the range of 4.5-5.5 GHz, we demonstrate a spatial resolution of 0.1 m, which is 50 times better than the previously reported results...